Safety ski binding

ABSTRACT

A safety ski binding for releasably securing a ski to the toe and heel portions of a ski boot. The toe portion of the binding includes a spring-biased plunger mounted on the ski and movable into engagement with the toe of the boot, and the heel portion of the binding includes a pair of spring-biased plungers mounted on the ski and movable into engagement with the heel of the boot. The toe and heel engaging plungers are each inclined downwardly toward the upper surface of the ski, and the heel engaging plungers are also inclined inwardly toward the longitudinal center line of the ski. Ball bearings are rotatably and shiftably mounted in the ends of the plungers in such a way as to reduce the force required to effect engagement of the ski with the boot but to require a greater force to effect disengagement.

United States Patent [72] Inventors Bernhard W. Klein;

Gunter L. Steves, both of St. Charles, 111. [21] Appl. No. 867,273 [22] Filed Oct. 17, 1969 [45] Patented Dec. 28, 1971 [73] Assignee Trans-World Ski-Equip, Inc.

St. Charles, Ill.

[54] SAFETY SKI BINDING 3,338,587 8/1967 Wiley ..280/ll.35l-IA 3,504,922 4/1970 Wiley 280/1l.35

Primary ExaminerBenjamin Hersh Assistant Examiner-Robert R. Song Attorney-Bibben, Noyes & Bicknell ABSTRACT: A safety ski binding for releasably securing a ski to the toe and heel portions of a ski boot. The toe portion of the binding includes a spring-biased plunger mounted on the ski and movable into engagement with the toe of the boot, and the heel portion of the binding includes a pair of spring-biased plungers mounted on the ski and movable into engagement with the heel of the boot. The toe and heel engaging plungers are each inclined downwardly toward the upper surface of the ski, and the heel engaging plungers are also inclined inwardly toward the longitudinal center line of the ski. Ball bearings are rotatably and shiftably mounted in the ends of the plungers in such a way as to reduce the force required to effect engagement of the ski with the boot but to require a greater force to effect disengagement.

SAFETY SKI BINDING This invention relates to ski bindings, and more particularly relates to a safety ski binding for automatically releasing an associated ski from a skiers boot whenever a predetermined maximum force is exerted upon the binding by the ski or boot.

Various types of ski bindings have been heretofore advanced for releasably securing a ski to a skiers boot, and which automatically release the ski from the boot whenever a predetermined maximum or abnormal force is exerted on the binding from either the ski or the boot. While many of such bindings have proved satisfactory for the intended purpose, others have not for various reasons such as complexity of construction and operation, necessity for frequent adjustment, exposure of the working parts of the binding to the elements with resulting premature deterioration, and unreliability of operation.

Accordingly, it is the general object of the present invention to provide a novel and improved safety ski binding which overcomes the aforementioned disadvantages and deficiencies.

Another object is to provide a novel safety ski binding, which will automatically release an associated ski from an associated boot whenever the binding is subjected to a predetermined maximum force from substantially any direction.

A more particular object is to provide a novel safety ski binding, wherein a plurality of axially shiftable plungers are utilized to releasably secure an associated ski to an associated boot and wherein at least a pair of said plungers are biased into engagement with the heel of the boot with the axes of the plungers inclined inwardly toward the longitudinal center line of the ski and downwardly toward the upper surface of the ski when the ski is fully engaged with the boot.

A further object is to provide a novel safety ski binding of the foregoing character, wherein at least one axially shiftable plunger is utilized to releasably secure the ski to the toe of the boot and wherein the axis of movement of the plunger is also inclined downwardly toward the upper surface of the ski when the ski is fully engaged with the boot.

A still further object is to provide a novel safety ski binding having at least one axially shiftable, spring-biased plunger for engaging and releasably securing an associated ski to an associated boot, wherein a bearing is mounted in the end of the plunger in such a way as to reduce the force required to effect engagement of the ski with the boot but to require a greater force to effect disengagement.

Other objects and advantages of the invention will become apparent from the following detailed description and accompanying sheets of drawings, wherein:

FIG. 1 is a broken, side elevational view of the central portion of a ski and the toe and heel portions of a boot, and showing a safety ski binding embodying the features of the present invention as it would appear when mounted on the central portion of the ski and engaged with the toe and heel portions of the boot;

FIG. 2 is a top plan view, with a portion thereof in section, taken substantially along the line 22 of FIG. 1;

FIG. 3 is a longitudinal sectional view along the line 3-3 of FIG. 2;

FIG. 4 is an end elevational view from the left end of the boot toe-retaining portion of the binding illustrated in FIG. 3;

FIG. 5 is an end elevational view of the boot toe mounted part of the portion of the binding illustrated in FIG. 3;

FIG. 6 is an end elevational view of the boot heel mounted part of the boot heel-retaining portion of the binding, and showing other parts of the binding and boot in phantom lines;

FIG. 7 is a top plan view of the boot heel mounted portion of the binding illustrated in FIG. 6, and showing other parts of the binding and boot in phantom lines;

FIG. 8 is a sectional view, taken substantially along the line 8-8 of FIG. 7; and

FIG. 9 is an enlarged, fragmentary, longitudinal sectional view of the boot-engaging end of one of the plungers of the binding, and showing additional details of the construction thereof.

Briefly described, the present invention contemplates a novel safety ski binding that is adapted to releasably secure an associated ski to an associated ski boot so that the ski will be automatically released from the boot whenever a predetermined force is exerted on the binding by the ski and/or the boot. The binding thus comprises first and second connecting means that are respectively adapted to releasably secure the ski to the toeand heel-portions of the boot, To this end, each connecting means includes a ski-mounted portion and a bootmounted portion. The ski-mounted portion of the first connecting means includes at least one axially shiftable plunger biased toward the boot-mounted portion, and the ski-mounted portion of the second connecting means includes a pair of axially shiftable plungers biased toward the boot-mounted portion and symmetrically disposed on opposite sides of the longitudinal center line of the ski.

The axis of movement of the plunger of the first connecting means is preferably coplanar with the longitudinal center line of the ski and is inclined downwardly toward the upper surface thereof. The axes of movement of the plungers of the second connecting means are also preferably inclined downwardly with respect to the upper surface of the ski and are inclined inwardly toward the longitudinal center line of the ski. The force biasing the plungers of the first and second connecting means toward the boot is provided by springs, there being one spring in the first connecting means for biasing the plunger toward the boot and two springs in the second connecting means for biasing the plungers toward the boot. The force exerted by the springs on their respective plungers is adjustable.

Each of the plungers of the binding is provided with antifriction means in the form of a rotatably mounted ball in the bootengaging end thereof. The ball is mounted in a bearing cavity in the end of the plunger, and the bearing cavity has a bearing seat of substantial area at its inner end and an annular inturned lip around the outer end thereof, The lip retains the ball in the cavity when the ski is disconnected from the boot and also acts as a seal to prevent the entry of foreign material into the cavity. To this end, a spring is provided in the bearing cavity for urging the ball outwardly into an inoperative position engaging the retaining lip.

The spacing between the bearing seat and lip is such that the ball will shift slightly in its cavity during engagement of the ski with the boot from its inoperative position engaging the lip to an operative position engaging the bearing seat. Such shift reduces the force required to effect rotation of the ball and consequently the force required to effect engagement of the ski with the boot. However, after the ski is connected to the boot, the ball rests on its seat, which is of substantially greater area than the area of the retaining lip. Consequently, a larger force is required to rotate the ball and cause disconnection of the ski from the boot.

Alignment of the ends of the plungers of the ski mounted portion of the second connecting means with the bootmounted portion is assured by guide means in the form of a pair of vertically extending grooves in the boot-mounted portion of the second connecting means.

In FIGS. 1 and 2, the central portion, indicated at 11, of a ski l2, is-illustrated. The toe portion, indicated at 13, and heel portion, indicated at 14, of a ski boot are also shown positioned on the central portion 11 of the ski and releasably secured thereto by a safety ski binding embodying the features of the present invention. The binding illustrated in FIGS. 1 and 2 thus comprises first connecting means, indicated generally at 16, that is adapted to releasably secure the toe portion 13 of the boot to the ski l2, and second connecting means, indicated generally at 17, that is adapted to engage and releasably secure the heel portion 14 of the boot to the ski.

The first connecting means 16 includes a portion 18 that is adapted to be mounted on the upper surface, indicated at 19, of the central portion 11 of the ski 12, and another portion 21 that is adapted to be mounted on the toe portion 13 of the boot. Specifically, the portion 21 of the binding is adapted to be mounted on the front end face, indicated in phantom lines at 22 in FIG. 2, and the sole of the boot at the toe portion 13 thereof. The second connecting means 17 likewise includes a portion 24 that is adapted to be mounted on the upper surface 19 of the central portion 11 of the ski, and another portion 25 that is adapted to be mounted on the rear end face, indicated in phantom lines at 26 in FIG. 2, and the sole of the boot at the heel portion 14 thereof.

Referring now to FIGS. 3,4 and 5, in connection with FIGS 1 and 2, it will be seen that the ski-mounted portion 18 of the first connecting means 16 comprises a casting having a platelike base or mounting section 27 and a cylindrical section 28 disposed above the base section 27. As best seen in FIG. 2, the base section 27 is generally diamond-shaped in plan and is of somewhat greater lateral width than the diameter of the cylindrical section 28 so as to provide areas on either side thereof for receiving screws, indicated at 31, which secure the casting to the upper surface 19 of the ski 12.

The cylindrical section 28 of the ski-mounted portion 18 is provided with a bore 32 therein in which a plunger 33 is slidably mounted. The axis of the bore 32 and plunger 33 is indicated by the line 34 in FIGS. 1 and 3. Such axis preferably lies in a vertical plane through the longitudinal centerline, indicated at 36 in FIG. 2, of the ski 12 when the portion 18 is mounted on the upper surface 19 of the ski. In addition, the axis 34 is preferably inclined downwardly toward the upper surface 19 of the ski 12 by an angle of about when so mounted.

In order to provide a force biasing the plunger 33 outwardly in its bore 32 and toward the toe portion 13 of the associated ski boot, a coil spring 37 is mounted in the bore 32 with one end of the spring bearing against the inner end of the plunger 33 and the other end of the spring bearing against the inner face of a plug 38 threaded into the outer end of the bore 32. The force exerted by the spring 37 on the plunger 33 and hence by the plunger 33 on the toe portion of the associated boot may be adjusted by threading the plug 38 into or out of the end of the bore 32. To this end, the outer end face of the plug 38 may be provided with an hexagonal-shaped recess or socket 39 for receiving an appropriately-shaped tooi (not shown) for manipulating the plug 38. Disengagement of the plunger 33 from the right end of the bore 32 is prevented by an external shoulder 42 (FIG. 3) on the plunger 33, which engages an internal shoulder 43 at the right end of the bore 32, as viewed in FIG. 3. The shoulder 43 is provided by a reduced diameter portion 44 of the bore 32.

In order to facilitate engagement of the ski 12 with the associated boot, the ski-mounted portion 18 includes means for retracting the plunger 33 in its bore 32 and compressing the spring 37 to some extent prior to engagement of the ski 32 with the boot. Such means, in the present instance, comprises a pivotally mounted lever 47 on the portion 18 of the first connecting means 16. The lever 47 is preferably formed with a bifurcated end 48 and is pivotally secured to the portion 18 as by screws 52 which extend through the portions of the bifurcated end 48 and are threaded into the casting. A cross pin 53 having its ends mounted in the bifurcated end portions of the lever, extends through an arcuate slot 54 in the cylindrical section 28 and through a cross bore of the plunger 73. Thus, pivotal movement of the outer or free end, indicated at 55, of the lever 47 from the full to the broken line position thereof in FIG. 1 will cause the plunger 33 to retract in its bore and in so doing will relieve some of the force exerted by the spring 37 on the plunger 33 tending to bias the plunger into engagement with the toe portion 13 of the boot. The effort required on the part of the skier to effect engagement of the ski 12 with the boot is thus substantially reduced. After the ski is connected to the boot, downward pressure on the free end 55 of the lever is, of course, released. Downward movement of the free end 55 of the lever 47 may be conveniently effected by either of the skiers poles.

In order to minimize friction between the portions 18 and 21 of the first connecting means 16 during engagement of the ski 12 with the boot and to assure accurate indexing of the toe portion 13 with respect to the longitudinal centerline 36 of the ski 12, a bearing in the form of a ball 56 is rotatably mounted in the outer end of the plunger. To this end, the outer end of the plunger 33 is provided with a cavity, indicated generally at 57, for receiving the ball 56. The inner end of the cavity 57 is concave to provide a generally hemispherical bearing seat 58 for the ball 56, which is preferably of the same radius of curvature as the ball. The outer end of the cavity 57 is provided with an annular, intumed lip 59 for retaining the ball 56 in the cavity 57. The lip 59 is preferably formed by rolling or otherwise inwardly deforming the material of the outer end of the plunger 33, and the inner diameter of the lip 59 is somewhat smaller than the diameter of the ball 56 so as to retain the ball in the cavity 57. The lip 59 also serves as a seal to prevent dirt, moisture and other materials from entering the cavity 57 when the ball 56 is engaged with the lip. A coil spring 62 is mounted in a bore 63 in the plunger 33, the spring 62 providing a biasing force urging the ball bearing 56 toward the retaining lip 59 As heretofore mentioned, the first connecting means 16 also includes the boot-mounted portion 21. Such portion 21, in the present instance, comprises an upright plate section 66 that is adapted to engage and be secured to the front end face 22 of the boot toe as by a screw (not shown). As shown, the boot-mounted portion 21 also includes a base or flange section 67 that is adapted to be secured to the underside of the sole of the boot as by a screw (also not shown). The plate section 66 of the portion 21 is shown as being bent so as to be slightly V-shaped in horizontal cross section. However, the plate section 66 could also be flat or arcuate in horizontal cross section in order to confomi to the contour of the outer surface of the front end face 22 of the boot.

In order to assure proper lateral indexing of the toe portion 13 of the boot when the ski 12 is connected thereto, the plate section 66 is provided with a bearing surface or seat 68 (FIGS. 3 and 5) which is preferably formed in the central portion of the upper edge, indicated at 72, of the plate section 66 and which extends into the outer surface, indicated at 73, of the plate section 66. The bearing surface 68 is preferably concave and has the same radius of curvature as the ball 56.

Referring now to FIGS. 6, 7 and 8 in conjunction with FIGS. 1 and 2, it will be seen that the ski-mounted portion 24 of the second connecting means 17 also comprises a casting having a plate-like base or mounting section 77 and a pair of cylindrical sections 78 and 79 spaced above the mounting section 77 by an interconnecting web or support section 80. As best seen in FIG. 2, the base section 77 is generally heel-shaped in plan and has a lateral width substantially equal to the width of the central portion 11 of the ski 12. The ski-mounted portion 24 may be secured to the upper surface 19 of the ski 12 by screws 81 which extend through the base section 77 and web or support section 80. The components and construction of the cylindrical sections 78 and 79 are identical, and therefore only the section 79 is shown in detail.

Thus, the cylindrical section 79 of the ski-mounted portion 24 is provided with a bore 82 therein in which a plunger 83 is slidably mounted. The axes of the bore 82 and plunger 83, as well as the axis of the bore and plunger 83 in the cylindrical section 78, are indicated by the lines 84 in FIG. 2. The plungers 83 of the cylindrical sections 78 and 79, and hence their axes 84, are disposed on opposite sides of the longitudinal cen terline 36 of the ski 12 in symmetrical relation, and are inclined inwardly toward the centerline 36 so that the included angle between the axes 84 is about 26. In addition, the axes 84 are preferably inclined downwardly toward the upper surface 19 of the central section 11 of the ski by an angle of about 5.

The plunger 83 of each cylindrical section 78 and 79 is biased outwardly of its bore 82 and toward the heel portion 14 of the boot by a coil spring 87 mounted in the bore 82. One end of each spring 87 bears against the inner end of the plunger 83 and the other end of the spring bears against the inner face of a plug 88 threaded into the outer end of the bore 82. Thus, the force exerted by each of the springs 87 on the plungers 83 may be adjusted by threading the plugs 88 into or out of the outer ends of their respective bores 82. To this end, the outer end face of each plug 89 may be provided with a hexagonally shaped recess or socket 89 for receiving an appropriately-shaped tool (not shown) for manipulating the plug 89 Disengagement of the plungers 83 from the inner or left ends of their respective bores 82 is prevented by an external shoulder 92 on each plunger, which engages an internal shoulder 93 at the inner or left end of each bore 82, as viewed in FIG. 2. The shoulders 93 are provided by a reduced diameter portion 94 at the inner ends of the shoes 82.

In order to minimize friction between the portions 24 and of the second connecting means during engagement of the ski 12 with the boot and to assure accurate indexing of the heel portion 14 thereof with respect to the longitudinal center line of the ski, a bearing in the form of a ball 96 is rotatably mounted in the outer end of each plunger 83. To this end, the outer end of each plunger 83 is provided with a cavity, indicated generally at 97, for receiving the ball 96. The inner end of the cavity 97 is concave to provide a generally hemispherical bearing seat 98, which is preferably of the same radius of curvature as the ball 96. The outer end of each cavity 97 is provided with an annular, intumed lip 99 for retaining the ball 56 in the cavity 97. The lip 99 is preferably formed by rolling or otherwise inwardly deforming the material of the outer end of the plunger 83, and the inner diameter of the lip 99 is somewhat smaller than the diameter of the ball 96 so as to retain the ball in the cavity 97. The lip 99 also serves as a seal to prevent dirt, moisture and other materials from entering the cavity 97 when the ball 96 is engaged with the lip.

A coil spring 102 is mounted in a bore 103 in each plunger 83, the spring 102 providing a biasing force urging the ball 96 outwardly of the cavity 97 and into engagement with the retaining lip 99.

As heretofore mentioned, the second connecting means 17 also includes the boot'mounted portion 25. The portion 25, in the present instance, comprises an upright plate section 106 (FIGS. 1, 2 and 6-8, inclusive) that is adapted to engage and be secured to the rear end face 26 of the boot heel as by a screw (not shown). As shown, the boot-mounted portion 25 also includes a base or flange section 107 that is adapted to be secured to the underside of the sole of the boot as by screws (also not shown). The plate section 106 is shown as being bent so as to be slightly V-shaped in horizontal cross section. However, the plate section 106 could also be flat or arcuate in horizontal cross section in order to conform to the contour of the outer surface of the outer end face 26 of the particular boot.

In order to provide a bearing surface on the plate section 106 against which the balls 96 of the portion 24 of the second connecting means 17 may bear, the upper edge of the plate section 106 is provided with a concave recess 108 (FIGS. 1, 2 and 6-8) having a radius of curvature equal to that of the balls 96. The recess 108 includes angularly inclined portions 111 and 112 (FIGS. 2 and 7) which preferably extend perpendicular to the axes 84 of their respective plungers 83 in the cylindrical sections 78 and 79. In order to provide the aforementioned angular relation between the portions 111 and 112, the plate section 106 is shown as being bent so that the included angle between the two bent parts thereof is substantially equal to the supplement of the included angle between the axes 84 of the plungers 83.

In order to facilitate alignment of the portion 25 of the second connecting means 17 with the portion 24 thereof during engagement of the ski 12 with the boot, the portion 25 is provided with guide means which coact with the balls 96 of the plungers 83 for this purpose. Such guide means, in the present instance, comprises a pair of vertically extending grooves 113 and 114 in the outer surface, indicated at 116, of the plate section 106. The grooves 113 and 114 extend from the lower edge of the plate section 106 into the angularly inclined portions 11] and 112, respectively, of the bearing surface 108.

As heretofore mentioned, the safety ski binding is adapted to facilitate engagement of an associated ski with an associated boot by reducing the force required to effect such engagement. However, once engagement has been effected, a greater force is required to effect disengagement. Thus, momentary inertia forces will not cause the binding to premature- 1y release the ski. The manner by which the foregoing is accomplished will best be understood by referring to FIG. 9.

In FIG. 9, the outer or ball bearing end of the plunger 33 is shown on a somewhat enlarged scale, as it would appear prior to engagement of an associated ski with an associated boot. It will be understood that while the following description makes reference to the plunger 33 and the parts thereof, it also applies to the plungers 83 of the portion 24 since the same mode of operation is present in all three plungers of the binding. Thus, the outer end of the plunger 33 includes the cavity 57 having the ball 56. The outer end of the cavity is provided with the intumed lip 59 for retaining the ball 56, and the inner end of the cavity 57 is provided with the generally hemispherical bearing seat 58. The coil spring 62 engages the ball 56 and urges it outwardly into engagement with the lip 59. The cavity 57 is sized so that the ball 56 does not engage the lip 59 at the same time that it rests on the seat 58. In other words, the seat 58 and lip 59 are spaced so that the ball 56 has to shift axially in the cavity 57 a slight amount in order to contact either the bearing seat 58 or the lip 59. The foregoing structural relationship is illustrated by the exaggerated clearance between the seat 58 and the ball 56 in FIG. 9.

Thus, assuming that the ball 56 is engaged with the lip 59, as in FIG. 9, and the skier steps into the binding to engage the ski with the boot, the initial contact of the ball 56 with the toe plate 21 will cause the ball 56 to shift from its engaged position with the lip 59 to an engaged position with the seat 58. Such shift causes the coefficient of friction of the ball 56in the cavity 57 to change from static to dynamic. Consequently, when the ball 56 engages the seat 58, it is already rotating or at least moving, and less effort is therefore required to complete engagement of the ski with the boot than would be required if the ball 56 were engaged with the seat 58 at the time it initially contacted the toe plate 21. Conversely, once the ski is completely engaged with the binding, a greater force is required to start the ball rotating and hence to effect relative movement between the ski and boot-mounted parts of the binding. Such additional force increment is beneficial in resisting small forces of short duration that are intermittently applied to the binding during skiing.

In summary, it will be apparent that the first and second connecting means 16 and 17, respectively, of the safety ski binding herein disclosed, provide a three point retention for releasably securing an associated ski to an associated ski boot. In addition, the binding may be easily and precisely adjusted to release the ski whenever a predetermined force is exerted on the binding by the ski and/or the boot, merely by threading the plug 33 and/or the plugs 88 into or out of their respective bores to obtain the desired spring force. Moreover, the aforementioned downward inclination of the axis 34 of the plunger 33, as well as the downward inclination of the axes 84 of the plungers 83, with respect to the upper surface 19 of the ski provides a force which at all times maintains contact between the undersurface of the boot and the upper surface 19 of the ski 12. Lastly, the novel mounting of the ball bearings in the ends of the plungers 33 and 83 reduces the force required to effect engagement of an associated ski with the boot, but requires a somewhat greater force to effect disengagement, which force is in addition to the force imposed by the springs 37 and 87.

Iclaim:

1. A safety ski binding adapted to releasably secure an as sociated ski to an associated ski boot having a toe and heel, said binding comprising first connecting means including a portion adapted to be mounted on said ski and to engage the toe of said boot, and second connecting means including a portion adapted to be mounted on said ski and another portion adapted to be mounted on the heel of said boot, said portion of said second connecting means including a pair of axially shiftable plungers disposed on opposite sides of the iongitudinal centerline of said ski and adapted to have their axes inclined inwardly toward said longitudinal centerline, said plungers being biased toward and having ends adapted to yieldably engage a bearing surface on said other portion of said second connecting means, and said other portion of said second connecting means having a pair of vertically extending, horizontally spaced grooves for guiding the ends of said plungers onto said bearing surface.

2. The safety ski binding of claim 1, further characterized in that other portion of said second connecting means comprises an upright plate having an upper edge and an outer surface, said bearing surface is provided at the upper edge of said plate, and said grooves are formed in the outer surface of said other portion.

3. The safety ski binding of claim 2, further characterized in that said upright plate is bent so that said bearing surface includes two portions, each of which is disposed generally perpendicular to the axis of its respective plunger.

4. In a safety ski binding adapted to releasably secure an associated ski to an associated ski boot, said binding including at least one axially shiftable plunger having an end adapted to engage a portion of said boot, the improvement comprising a rotatably mounted bearing in said end of said plunger, said bearing also being shiftable between operative and inoperative positions in said end, and means biasing said bearing toward said inoperative position, said biasing means being yieldable and permitting-said bearing to shift from its inoperative to its operative position during engagement of said ski with said boot, whereby the frictional force resisting rotation of said bearing and consequently the force required to effect connection of said ski and said boot is reduced.

5. The safety ski binding of claim 4, further characterized in that said bearing is mounted in a cavity in said end of said plunger, said cavity has a bearing seat and a retaining lip spaced from said seat, and said bearing seat is of substantially greater area than said lip, whereby a greater force is required to effect rotation of said bearing on its seat and disengagement of said ski from said boot after said ski is connected to said boot than is required to effect engagement of said ski with said boot.

6. The safety ski binding of claim 5, further characterized in that said bearing seat is located at the axially inner end of said cavity, and said retaining lip is located at the axially outer end of said cavity.

7. The safety ski binding of claim 4, further characterized in that said bearing comprises a ball, said bearing seat is concave and of substantially the same radius of curvature as that of said ball, and said retaining lip comprises an annular inturned portion of the outer end of said plunger and having an inner diameter somewhat less than the diameter of said ball, said lip sealing the outer end of said cavity when said bearing is engaged therewith.

8. The safety ski binding of claim 4, further characterized in that said means biasing said bearing toward said lip comprises a spring carried by said plunger and engaging said bearing. 

1. A safety ski binding adapted to releasably secure an associated ski to an associated ski boot having a toe and heel, said binding comprising first connecting means including a portion adapted to be mounted on said ski and to engage the toe of said boot, and second connecting means including a portion adapted to be mounted on said ski and another portion adapted to be mounted on the heel of said boot, said portion of said second connecting means including a pair of axially shiftable plungers disposed on opposite sides of the longitudinal centerline of said ski and adapted to have their axes inclined inwardly toward said longitudinal centerline, said plungers being biased toward and having ends adapted to yieldably engage a bearing surface on said other portion of said second connecting means, and said other portion of said second connecting means having a pair of vertically extending, horizontally spaced grooves for guiding the ends of said plungers onto said bearing surface.
 2. The safety ski binding of claim 1, further characterized in that other portion of said seconD connecting means comprises an upright plate having an upper edge and an outer surface, said bearing surface is provided at the upper edge of said plate, and said grooves are formed in the outer surface of said other portion.
 3. The safety ski binding of claim 2, further characterized in that said upright plate is bent so that said bearing surface includes two portions, each of which is disposed generally perpendicular to the axis of its respective plunger.
 4. In a safety ski binding adapted to releasably secure an associated ski to an associated ski boot, said binding including at least one axially shiftable plunger having an end adapted to engage a portion of said boot, the improvement comprising a rotatably mounted bearing in said end of said plunger, said bearing also being shiftable between operative and inoperative positions in said end, and means biasing said bearing toward said inoperative position, said biasing means being yieldable and permitting said bearing to shift from its inoperative to its operative position during engagement of said ski with said boot, whereby the frictional force resisting rotation of said bearing and consequently the force required to effect connection of said ski and said boot is reduced.
 5. The safety ski binding of claim 4, further characterized in that said bearing is mounted in a cavity in said end of said plunger, said cavity has a bearing seat and a retaining lip spaced from said seat, and said bearing seat is of substantially greater area than said lip, whereby a greater force is required to effect rotation of said bearing on its seat and disengagement of said ski from said boot after said ski is connected to said boot than is required to effect engagement of said ski with said boot.
 6. The safety ski binding of claim 5, further characterized in that said bearing seat is located at the axially inner end of said cavity, and said retaining lip is located at the axially outer end of said cavity.
 7. The safety ski binding of claim 4, further characterized in that said bearing comprises a ball, said bearing seat is concave and of substantially the same radius of curvature as that of said ball, and said retaining lip comprises an annular inturned portion of the outer end of said plunger and having an inner diameter somewhat less than the diameter of said ball, said lip sealing the outer end of said cavity when said bearing is engaged therewith.
 8. The safety ski binding of claim 4, further characterized in that said means biasing said bearing toward said lip comprises a spring carried by said plunger and engaging said bearing. 